It is known in the art to print thick film conductive inks on a substrate and cure the inks to produce an electrical circuit assembly. Various resistivities of the conductive ink are used and additional electrical components may be attached to the substrate to manufacture the electrical circuit. Polymer thick film circuits may be manufactured using a polyester dielectric substrate and screen printed thick film conductive inks. High speed screen printing techniques can be used, and multi-layer circuits may be manufactured utilizing dielectric materials as insulating layers. Both active and passive surface mount components can be added to the substrate. The substrate with the mounted components can be encapsulated to shield the assembly from the effects of moisture.
Alumina (Al2O3) is often utilized as a ceramic substrate for the printing of thick film circuits thereon. Passive and active components can be mounted to conductive pads screen printed on the substrate. The alumina substrate is typically a planar rectangular shaped substrate. Alumina is a widely used material due to availability, relatively low cost and stable physical properties. It is relatively easy to fabricate and retains its strength at high temperatures.
Alumina can be manufactured in thicknesses from 0.5 mm up to 12.5 mm. The power density in watts/cm2 for alumina is approximately 23.25 W/cm2. Alumina also has a relatively high dielectric strength of 2.39×105 V/in and an electrical resistivity of 3.28×1013 Ohms ft.
It is known to encapsulate or contain high voltage circuits in an enclosure filled with oil having a high dielectric and breakdown characteristic, to allow the proximity of high voltage components in the assembly. High voltage circuits can be pre-positioned by way of a printed circuit board or point-to-point wiring, and the completed assembly encapsulated to allow safe installation into another assembly.
Current known methods of assembling electrical circuit components involve the connection of leads of the electrical component to an intermediate structure, such as a solder post or a solder pad of a printed circuit board. The lead of the electrical component typically is formed so that it can be inserted into a hole in the printed circuit board, and the lead then soldered to a pre-tinned pad on the circuit board. If the lead is to be connected to a solder post, the lead is bent around the post and then soldered thereto. Solder posts typically have leads of other components or wires soldered thereto.
Although rarely known to be done in production electrical assemblies, leads of electrical components can be directly soldered together without the support of a solder post or a printed circuit board. Typically the leads are twisted together by hand, and solder is applied to the twisted leads to ensure the electrical connection.
Leadless electrical components are placed on surface mount circuit boards and are held in place with a small amount of adhesive. The ends of the leadless components are then soldered to pads on the circuit board, which provides mechanical support and electrical connections for the leadless component.
Each of the known methods described above requires a mechanical attachment of either the leads or the component prior to soldering.
What is needed in the art is an assembly method that results in pre-positioned electrical components without the use of an attachment procedure.